Wireless communication networks are currently used for a broad range of business and personal communications needs. Wireless network subscribers have grown accustomed to ready access to telephone, messaging, and data services regardless subscriber location or subscriber travel. Because of the increased reliance of subscribers on wireless networks, subscribers insist on services being available at all times at any arbitrary location. Unfortunately, network design can occasionally be inadequate to provide a requested service, frustrating network subscriber.
While network operators have long emphasized providing reliable services to their subscribers, diagnosing the reasons for any particular communication problem is difficult. In many wireless networks, dropped calls or other missed or incomplete data or voice communications are associated with limitations to network coverage. Limited coverage problems arise because of local topography (e.g., hills) or structures (office towers) that block or obscure some portions of a coverage area (typically one or more cells) from receiving suitable radio signals from a network radio tower or other transmitter. In some cases, tower placement is less than ideal because of an inability to secure necessary property permissions, or any of a variety of other practical or political reasons result in cell towers unavoidably being placed in locations that provide less than optimum continuous coverage. Thus, “holes” in coverage are creates in which subscriber mobile stations are either too far away from cell towers or are blocked or partially blocked from cell towers by terrain or buildings. These holes appear as dead spots where mobile stations are unable to acquire a sufficient signal to sustain two-way communications. A user of a mobile station entering one of these holes while engaged in a call will often experience progressively worsening signal reception, resulting in either disruptions in communications or call termination.
Other communications problems are associated with a number of subscribers using the network or requesting network services. For example, in some wireless networks, unique sets of radio frequencies are assigned to each base station. Because only a finite number of frequencies are available, frequencies are used at multiple base stations and are generally allocated according to frequency reuse plans in order to avoid different signals on the same frequency from appearing at the same transmitter or receiver. Although an ideal frequency reuse plan can be derived from propagation models, such a plan is only effective to the extent cell arrangement reflects an idealized layout where each cell is spaced according to a uniform honeycomb pattern, with all cells having the same geographic elevation and flat topography. In practice, cells are irregularly shaped and spaced, yielding to the varying nature of terrain and the practicalities of securing suitable base station locations. Even an ideal layout cannot prevent more than one radio signal at a common frequency from appearing in a particular cell, but merely provides reduced amplitudes of any unwanted radio frequency signals. Thus, so-called co-channel interference arises when two or more different transmitting stations (mobile or stationary) in relatively proximate areas both use the same radio frequency channel. Like holes in coverage, co-channel interference can produce degraded signal reception or call termination.
Network operators strive to prevent dropped calls and other missed communications due to limited network coverage or excess communication demand. For holes in geographic coverage, wireless operators can install additional transmitter or change a location or transmission direction of an existing transmitter. Co-channel interference effect can be reduced base on, for example, adjustments to a frequency reuse plan. However, for such modifications to be effective, the source of any communications limitations should be identified as being associated with coverage deficiencies or capacity limits. Conventional methods of assessing network performance are based on drive tests in which a transmitter/receiver is driven through a network coverage area. Such drive testing is slow, expensive. Therefore, improved methods of diagnosing network communication limitations are needed.